チタン酸ストロンチウム系半導体コンデンサーの粒界構造のTEM観察

概要

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Structures of grain boundaries of SrTiO_3 semiconductive capacitor have not been fully elucidated. Several studies were focused on the SrTiO_3 systems which include additives, such as, Al_2O_3 or SiO_2. In this study, we first investigated the grain boundaries of Sr_<0.975>Ca_<0.025>TiNb_<0.004>O_3 which did not contain any additives. Then Bi_2O_3/CuO, which is a grain boundary modifier, was also added in order to investigate the process that changes grain boundaries into insulators. Samples heat-treated with Bi_2O_3/CuO were quenched in water and TEM (transmission electron microscopy) was carried out on these microstructures. Grain boundaries of samples sintered in a reduced atmosphere showed segregation of TiO_2 oxide phase, which included no traces of Sr. On the other hand, in grain boundaries of samples heat-treated with the Bi_2O_3/CuO agent, at least two phases existed. One phase included large amounts of Bi and Cu, while the other phase showed only traces of these elements. Near the grain boundaries Bi and Cu diffused into the matrix grains showing inhomogeneous diffusion of which diffusion lengths were different at each side of the grain boundary and seemingly lattice coincident with both grain boundary layers and matrix grains. In addition, steps of about 2 nm in height were observed at grain boundaries.
社団法人日本セラミックス協会の論文
2000-07-01